Session Initiation Protocol (SIP) is a call control signaling protocol for Internet Protocol (IP) network. SIP is designed to be device-agnostic—that is, it is intended to provide a highly flexible call signaling capability that is not tailored to the capabilities of any particular device. Analog telephone signaling, on the other hand, is device-specific and highly constrained because of the historical legacy of the services delivered to the device. As a result, many call features available in traditional analog telephone devices (e.g., notification of end terminals status) are not easily integrated in a SIP-based network because SIP-based network elements may communicate only to adjacent SIP-based network elements. For example, one or more SIP messages may be transmitted between end terminal A and end terminal B to establish a SIP session (e.g., call session). Currently, an initiation process of a SIP session between end terminal A (e.g., caller) and end terminal B (e.g., callee) may take a long period of time (e.g., minutes). During the initiation process, SIP service providers may not be capable of determining whether a valid SIP session has been established between end terminal A and end terminal B. For example, the SIP service providers may receive one or more messages from intermediate devices between end terminal A and end terminal B, however, SIP service providers may not take any action for a long time until receiving one or more messages from the end terminal B. Therefore, the SIP service providers may have to wait for a long period of time before taking one or more actions associated with the initiation process of the SIP session.
These and other embodiments and advantages will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the various exemplary embodiments.